This invention relates to engine camshafts including assembled camshafts and, more particularly, to an apparatus and method for checking the phase angle location of the cam lobes of a camshaft relative to a timing indicator on the camshaft.
It is known in the art of camshaft manufacture to form a camshaft by assembly of a plurality of cam lobes and bearing members onto a hollow tube and fixing the components in place by any one of various assembly processes. In one example, the cams and bearings are placed in a fixture which holds these components in predetermined angular relationships, a tubular shaft is inserted through aligned central openings in the cam and bearing components and the tube is expanded into engagement with the openings by forcing a steel ball through the tubular interior of the tube.
Because of the possibility that one or more of the lobes may be accidentally mispositioned or mislocated in the fixture, or the fixture itself may become worn excessively, it is desirable to maintain close inspection of the camshafts soon after the assembly process so that any fault in the process will be discovered before a number of unusable camshafts are manufactured. It has been a problem, however, to find a practical method of inspecting the camshafts which is easy to operate, can be accomplished soon after the assembly step and provides an accurate indication of the relative phase angles of the cams so that an operator is advised soon if any malfunction of the assembly process has occurred.
The present invention provides an apparatus and method which may be utilized by an operator for automatically verifying the lobe angle of a cam relative to the location of a timing notch on a camshaft. Each camshaft is picked up from a conveyor after assembly, held between centers and rotated. A plurality of lasers is provided, one for each cam lobe and one for the timing notch. The lasers are aligned with their associated lobes and timing notch and project a laser beam of light on each lobe and the notch. The light from these elements is focused, through one or more lenses, against a receiver in each laser unit which determines, by the position of the focused light, the distance of the lobe and notch surfaces at prescribed intervals from the receiver element.
The distance measurements are fed into a computer along with encoded information on the angular positions of the lobes as the camshaft is rotated, and the information is evaluated in a program which determines the relative angles of all the lobes to the timing notch. The readings are then internally compared to a reference lobe and the computer determines the accuracy of location of the other lobes relative to the reference lobe and the timing notch relative to the reference lobe. Parts with any deviation from the allowable tolerance are rejected and a warning is given to the operator to correct the process if required. The laser measurement process is more accurate and reliable than other forms of measurement and it does not rely on contact with the lobes so down time due to wear or damage to probes is avoided.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.